Add support for robolectric tests

[samartnik]

Description

Robolectric tests (https://chromium.googlesource.com/chromium/src/+/HEAD/docs/testing/android_test_instructions.md#robolectric-tests) are more lightweight and can be run for tablet related code, so we should integrate them to Brave codebase. Issue related to discussion in brave/brave-core#29087
Good point to start is to convert BraveHomepageSettingsTest to robolectric, like they have in the upstream.

Steps to reproduce

1. n/a

Actual result

n/a

Expected result

n/a

Reproduces how often

Easily reproduced

Brave version

n/a

Device

• Brand/model: n/a
• Android version: n/a

Channel information

• release (stable)
• beta
• nightly

Reproducibility

• with Brave Shields disabled
• with Brave Rewards disabled
• in the latest version of Chrome

Miscellaneous information

No response